1. Field of the Invention
The present invention relates to a novel positive type photosensitive resin composition and a method for forming a resist pattern.
2. Description of the Related Art
A positive type photosensitive resin composition has excellent characteristics in points of no environmental pollution, the saving of resources and energy, high production efficiency and the like, and for this reason, the composition has heretofore been used as a coating composition, an ink and an adhesive in many fields. This kind of photosensitive resin composition has been applied to use purposes in which circuit boards, plastics, lumbers, metals, papers, glasses, fibers and the like are used as materials.
However, when-such a positive type photosensitive resin composition is industrially produced and applied to a practical line, the following problems are present.
The positive type photosensitive resin composition intends to utilize a difference of solubility between an exposed portion and an unexposed portion.
With regard to an emission spectrum wavelength of a visible light which has heretofore been used for the exposure, for example, activated lights of 488 nm, 532 nm and the like have been usually used. In the case that such a photosensitive resin composition is handled, an electric lamp such as a fluorescent lamp colored by coating an outer tube thereof with a dark red colorant or by winding a dark red film around the outer tube is used as a safelight (a working lamp). Under the surroundings of such a dark red safelight, however, some problems are present. For example, it is difficult to inspect the state of a coating film after the coating, and it is not easy to check a coating apparatus, an irradiation apparatus, a conveying apparatus and the like. In consequence, safe working properties, a working efficiency, the quality stability of products and the like are poor.
The present invention has been developed for the purpose of developing a novel positive type photosensitive resin composition which can be handled under conditions of a bright safelight, and a method for forming a resist pattern by the use of this composition.
The present inventors have intensively researched with the intention of solving the above problems, and as a result, it has been found that combining a specific positive type photosensitive resin composition and a specific safelight can solve the conventional problems. In consequence, the present invention has been completed.
That is to say, the aspects of the present invention are as follows:
1. A liquid or a solid positive type photosensitive resin composition which is used under the irradiation circumstance of a safelight having a maximum wavelength within the range of 500 to 620 nm, wherein an absorbancy of an unexposed film formed from this composition is 0.5 or less within the range of the maximum wavelength xc2x130 nm selected from the range of the maximum wavelength of the safelight.
2. The above-mentioned positive type photosensitive resin composition which comprises a resin and a light acid generator for generating an acid radical by an active energy ray as essential components, the resin and the light acid generator being chemically bonded, or the resin and the light acid generator being mixed.
3. The above-mentioned positive type photosensitive resin composition wherein the safelight is given from a discharge lamp containing sodium as a main component (which consists mainly of a D-ray having a light wavelength of 589 nm).
4. A method for forming a resist pattern which comprises:
(1) a step of applying a positive type photosensitive resin composition onto a substrate to form a photosensitive film thereon,
(2) a step of exposing the photosensitive film formed on the substrate to a laser beam directly or through a mask film so that a desired resist pattern (an image) may be obtained on the photosensitive film, and
(3) a step of subjecting the resist film to a developing treatment to form the resist pattern on the substrate, wherein an absorbancy of an unexposed film formed from the positive type photosensitive resin composition is 0.5 or less within the range of a maximum wavelength xc2x130 nm selected in the range of the maximum wavelength of a safelight; and at least one step of the steps (1) to (3) is carried out under the irradiation circumstance of the safelight having a high spectral luminous efficiency in which the maximum wavelength of an emission spectrum of a light source is within the range of 500 to 620 nm.
5. The method for forming the resist pattern wherein the safelight is given from a discharge lamp containing sodium as a main component (which consists mainly of a D-ray having a light wavelength of 589 nm).
According to the present invention, it is possible to form a resist pattern which is remarkably excellent in safe operativity, operational efficiency, the quality stability of products, and the like.